The objectives of this project are to elucidate the biochemical mechanisms controlling the synthesis, storage, release, action and termination of action of neurotransmitters and to determine how genetic factors, environmental stimuli, or drugs influence these control mechanisms. During the last year, levels of plasma catecholamines in intact rats have been studied during a variety of stressful conditions in different genetic strains of rats and the relationship of sympathoadrenal responsivity related to behavioral parameters, blood pressure, and heart rate. The effects of chronic treatment with drugs which interfere with sympathetic nerve integrity were studied and the role of peripheral catecholamines in mediating tremor due to oxotremorine examined. The roles of presynaptic receptors in modulating release of norepinephrine from axonal sprouts of organ cultured ganglia were examined.